1. Field of the Invention
The invention relates to the field of reducing the temperature of combustion gases discharging to the atmosphere above a ship stack in a manner for attenuating the heat radiation thereof.
2. Brief Description of the Prior Art
Methods are known in the prior art to suppress infrared radiation of exposed hot metal parts and from hot gas plumes from jet engines to reduce their vulnerability to missile attack. Such is disclosed in U.S. Pat. No. 4,095,417 where ejector vanes introduce cooling ambient air into the hot engine exhaust and hide hot metal parts. U.S. Pat. No. 3,712,054 discloses a method of attenuating a heat radiation field of a heat exhausting vehicle by injecting fluidized foreign powdered material in the vicinity of heat radiation. It is further known to reduce stack temperatures on Navy ships by aspirating cooling air into the stack, and by spraying sea water into the presence of the hot exhaust gases for suppressing infrared radiation. Even to the present, it has always been ambient water at the temperature of the surroundings, which was sprayed into the stack. The idea was that the colder the water the better, because of the additional heat water at a lower temperature was capable of absorbing in its transition from water to vapor. The shortcoming of this reasoning is that the water would often enter the atmosphere from the stack incompletely vaporized in the form of droplets, and as such would radiate as a blackbody suspectable to detection. Stacks on modern ships are not tall enough to permit cold water to completely vaporize by the time it leaves the stack.